Field of the Invention
The present invention relates to an electromagnetic flow meter.
Priority is claimed on Japanese Patent Application No. 2015-254711, filed Dec. 25, 2015, the content of which is incorporated herein by reference.
Description of Related Art
All patents, patent applications, patent publications, scientific articles, and the like, which will hereinafter be cited or identified in the present application, will hereby be incorporated by reference in their entirety in order to describe more fully the state of the art to which the present invention pertains.
In a plant with various facilities, a plurality of field devices (measurement devices or operating devices) are installed for the purpose of performing monitoring of a state in which each of the facilities disposed in the plant is working or control of an operation of the facilities. An electromagnetic flow meter that is one measurement device in the field devices is installed in a pipe or the like disposed in a plant, measures a flow rate of a conductive fluid flowing in the installed pipe, and outputs information on the measured flow rate. Information on a flow rate of fluid output by this electromagnetic flow meter is used for control when fluid is caused to flow in a pipe using a pump or a valve that is one operating device in the field devices (control of driving of the pump or opening and closing of the valve).
Further, in order to perform secure work in the plant, daily or regular checking work for respective facilities and work for coping with problems such as failures or malfunction are performed. This work includes work for maintaining the integrity of the field devices installed in the respective facilities, that is, checking work for enabling a working state of the facility by the field device to be accurately measured. Conventionally, various technologies for verifying the integrity of the field device have been proposed.
For example, Japanese Unexamined Patent Publication No. 2002-195861 discloses a technology of an electromagnetic flow meter that diagnoses insulation deterioration of a plurality of electrodes (measurement electrodes) disposed in a liquid in order to measure a flow rate. In the technology disclosed in Japanese Unexamined Patent Publication No. 2002-195861, a flow rate value is individually calculated for each of the measurement electrodes based on flow rate signals output from the respective measurement electrodes according to a detected flow rate of fluid, and insulation deterioration is diagnosed for each of the measurement electrodes based on a relative error value of the calculated flow rates.
In a configuration of the electromagnetic flow meter disclosed in Japanese Unexamined Patent Publication No. 2002-195861, a flow rate value of fluid that the electromagnetic flow meter outputs as a result of measurement is obtained by obtaining a difference between respective flow rate signals output from the measurement electrodes. In this case, a process of obtaining the difference between the respective flow rate signals is performed using a differential amplifier. Therefore, from the electromagnetic flow meter having the configuration disclosed in Japanese Unexamined Patent Publication No. 2002-195861, a flow rate value obtained in a state in which noise of an in-phase component (for example, commercial noise) included in each flow rate signal has been removed by the differential amplifier is output as a result of measurement.
However, in the configuration of the electromagnetic flow meter disclosed in Japanese Unexamined Patent Publication No. 2002-195861, an individual flow value for diagnosing insulation deterioration is directly obtained from the flow rate signals output from the respective measurement electrodes. That is, in the electromagnetic flow meter having the configuration disclosed in Japanese Unexamined Patent Publication No. 2002-195861, the individual flow rate values are obtained in a state in which noise such as commercial noise included in each flow rate signal has not been removed. In the flow rate signal that each measurement electrode outputs, it is conceivable that information on an actual flow rate of fluid which should inherently have been detected may be hidden by noise. Therefore, in the electromagnetic flow meter having the configuration disclosed in Japanese Unexamined Patent Publication No. 2002-195861, the individual flow rate values of each measurement electrode which should inherently have been obtained may not be able to be accurately determined due to an influence of noise included in each of the flow rate signals. Therefore, in the technology disclosed in Japanese Unexamined Patent Publication No. 2002-195861, there is a problem in that it is not possible to accurately diagnose a state of the insulation deterioration of each of the measurement electrodes of the electromagnetic flow meter.